1. Field of the Invention
The present invention pertains to a vapor removal apparatus for a fuel supply system used in an internal combustion engine.
2. Description of the Related Art
As an internal combustion engine, an engine equipped with a fixed Venturi-type vaporizer 1 such as that shown in FIG. 5, for example, is known in the conventional art.
A fuel supply system that supplies fuel F held in a fuel tank 2 to the vaporizer 1 is mounted to the vaporizer 1.
The fuel supply system is equipped with a fuel supply path 4 that fluidically connects the fuel tank 2 with a float chamber 3 mounted to the vaporizer 1, and a fuel pump 5 coupled in the fuel supply path 4 to supply the fuel F from the fuel tank 2 to the float chamber 3.
In this type of fuel supply system, when the fuel F is sucked into the fuel pump 5, air bubbles may be generated in the suctioned fuel F due to negative pressure.
These air bubbles include vapor generated in the fuel F due to the increase in ambient temperature which accompanies the heating up of the engine. The term “vapor” refers generically to non-liquid gaseous material such as air bubbles and fuel vapor.
When the air bubbles and vapor are generated in this way, it is assumed that they will be supplied to the vaporizer 1 via the float chamber 3 together with the fuel F. When the fuel F in which the air bubbles and vapor are mixed is supplied to the vaporizer 1, the following problems occur: (1) an unstable air/fuel ratio in the air-fuel mixture generated in the vaporizer 1, and (2) difficulty in restarting the engine.
Accordingly, in an internal combustion engine in which a large amount of vapor or air bubbles are generated because the thermal ambient conditions are poor, or because the engine is susceptible to vibration, a vapor separation tank 6 that temporarily holds the fuel F sent from the fuel pump 5 is located downstream of the fuel pump 5 at a point in the fuel supply path 4, such that in this vapor separation tank 6, the vapor and air bubbles are separated so as to rise to the top of the vapor separation tank 6 due to their buoyancy, and the vapor and air bubbles are expelled toward the fuel tank 2 via the vapor return path 7 located at the top of the vapor separation tank 6.
However, in this conventional type of fuel supply system for an internal combustion engine, the following problem requiring correction remains.
That is, while the fuel F is being held in the vapor separation tank 6, the vapor and air bubbles are separated using their own buoyancy, but when the vapor separation tank 6 is shaken by engine vibration or for some other reason, the fuel F being held in the vapor separation tank 6 is churned. As a result, the vapor and air bubbles are not separated, and therefore, the vapor and air bubbles end up being sent into the vaporizer 1 together with the fuel F.